EDNRB and deafness: As presented by the variable severity of deafness in hearing impaired Wnt1Cre/Ednrb mutants (Figures 1A, 1B, and 1D), we predict that primary Ednrb-deficiency makes spiral ganglion glia vulnerable to additional and/or epistatic effects of other (modifier) genes, and which ultimately manifest impairment in synapse formation.